In computer modeling studies the relationships among DNA content distributions, cell kinetics, and cell morphology were explored and applied in a proposed functional classification for the lymphomas. In vitro studies of the effects of hydroxyurea and cytosine arabinoside were done in Sarcoma 180, exploring CxT effects on drug lethality, sublethal damage, and 3HTdR uptake. Studies were completed on the effects of Colcemid on hematopoiesis in mice, with special reference to its stimulatory effects on thrombopoiesis. Comparisons of methods of rapid radioautography were carried out. A commercial bacterial colony counter was adapted for semiautomated grain counting in smears, and cell counting in sections. Flow microfluorometry was used to perform multiparameter analysis of clinical samples. Although special emphasis has been placed on chronic lymphocytic leukemia, Sezary's syndrome and the lymphomas, a broad spectrum of tumors was studied. In vivo 3HTdR studies were carried out in four patients with Sezary's syndrome. Percent labelled mitosis curves and labelling indices were obtained in normal skin and Sezary's cells, and the labelling patterns of circulating Sezary's cells and granulocytes were studied. A treatment protocol for small cell carcimona was developed in collaboration with NCI-VA to explore applications of cell kinetics in clinical chemotherapy.